The focus of experiments in this project has been to identify and understand the developmental maturation of the cellular and subcellular mechanisms involved in the regulation of pituitary hormone secretion, in particular, prolactin (PRL), adrenocorticotrophin (ACTH), Beta-endorphin (Beta-end) and luteinizing hormone (LH). Specific studies are designed to elucidate the individual roles and interactions of monoaminergic neurotransmitters and neuropeptides in the neuroendocrine secretory control of these hormones from the anterior (AP) and neurointermediate (NIL) lobes of the pituitary, the sequential arrangement and functional connectivity of that neuronal circuitry, the developmental maturation of that circuitry, and the possible interaction that the AP and NIL undertake to achieve that neuroendocrine regulation. We have characterized and utilized the selective requisite developmental maturation of the PRL response to ether stress in order to determine which neurochemical responses are tied to that hormonal response. Pharmacological agents and specific antisera as well as lesioning and surgical procedures which selectively affect particular neurotransmitter or neuropeptide neurons are used to determine the individual contributions, sites of interaction, and functional neuronal connectivity of those specific components in the physiological regulation of these hormones. Both static in vitro incubations of AP, NIL, or whole pituitary tissues as well as dispersed AP cell procedures are utilized to determine the sites of action of the individual components as well as the possible interaction of NIL and AP in governing the release of the hormones. Measurements of neurotransmitter/neuropeptide function are made during experimental conditions when dynamic changes in the secretion of these hormones are occurring, including the proestrous surge, acute stressful and suckling stimuli, pharmacologically-induced changes in hormonal secretion, and experimentally-induced hyperprolactinemia.